1. Field of the Invention
The present invention relates to a power hand tool and more particularly, to an elbow-type power hand tool, such as cordless power screwdriver, power driller, etc.
2. Description of the Related Art
A conventional linear-type power hand tool, such as cordless power screwdriver, generally comprises a housing, an output shaft axially rotatably extended out of a front end of the housing for coupling a tool bit, a power drive, e.g. a DC motor, mounted inside the housing for rotating the output shaft, and a torque control mechanism, which comprises one or more planet gear trains and is connected between the motor shaft and the output shaft for regulating the output torque of the output shaft. The torque control mechanism further comprises a threaded adjustment ring axially moveably coupled to the housing, a plurality of steel balls rested on an outer surface of the ring gear of the planet gear train, and a coil spring squeezed between the adjustment ring and the steel balls. The ring gear is rotatably mounted in the housing; however, the ring gear is kept stationary in normal status because the steel balls forced by the spring tightly press on the outer surface of the ring gear to hold the ring gear unrotatable. If a user adjusts the position of the adjustment ring on the housing by rotating the adjustment ring, the spring power of the spring that pushes the steel balls will be adjusted, so that the maximum output torque of the power hand tool will be relatively adjusted. When the output shaft receives a resistance that exceeds the maximum output torque, the rotation of the output shaft is stopped. In the meantime, the power, which is continuously generated by the DC motor and transmitted by the motor shaft that serves as the sun gear of the planet gear train, will be transmitted to the ring gear through the planet gears to further rotate the ring gear such that no power is further outputted from the output shaft.
The housing of the power hand tool that is equipped with the aforesaid torque control mechanism needs to provide sufficient space for installation and movement of the adjustment ring. However, a conventional elbow-type power hand tool provides no sufficient space for the aforesaid torque control mechanism. Therefore, the conventional elbow-type power hand tool does not provide a torque adjustment function.